The OP said a few people a year die from shocks at this lake. Seems thats like having a serial killer in the neighborhood, and someone would have done a 'study' as to its causes.
I have never worked on a dock and hardly been on one, but I fail to see why this is any different than a pool deck or waterscaped yard with lights and pumps and outlets - except that its always in motion.
Such areas utilize GFCI's and normal grounding wires, and no one in planning or in the trades has ever suggested they have a equipotential ground plane installed. I think you mentioned 3x3 feet.
And RAJ, surely no one would consider the 'voltage drop' contributing to shocks and breaking the ground wire at the dock foot and adding ground rods. Thats a bit of hallucination.
I would guess your serial killer at the lake is old wiring that has wiggled up and down for many years in waves and storms and rubbed itself bare in conduit, to various values of danger. Attached to old standard breakers, perhaps without any ground at all.
I would wire my dock with some mine rated SJ 3 or 4 wire cord in pvc conduit with pvc flex and loops at the dock joints connected to modern GFCI breakers. Then I would liberally use silicone inside the boxes to partially encapsulate the wires to preclude motion. And all connections would be covered with an anti corrosive paste-grease.
A lot of work, which is why I dont have a dock and why people die at them.
Frankly, a standard extension cord zip tied to the dock rail and plugged into a GFCI would likely be safer than some old wires in flex or conduit that cannot be inspected for chaffing from motion. Ask Boeing, they worked this out years ago.
Ballvalve...et.al. Here's another link that discusses the exact same thing and in this discussion a "qualified" electrician is saying the very same thing about the tingle that I said way back there concerning voltage drop.
://www.electrical-contractor.net/forums/ubbthreads.php/topics/167411/2.html
Here's the part that I noticed in the thread...
Quote:
With the mains to the house, garage and dock off I still have the same current flow, yet neither the new copper ground rod at the meter, nor the poco ground, nor their guy wire show any current flow.
Did you remove the main bonding jumper for this test? The utility primary and secondary grounded conductors are connected together. In many cases like this the source of the voltage is the voltage drop on the utility primary neutral.
Don
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Don(resqcapt19)
As for some details on the electrocutions on this lake I would say that most have been due to frayed wires as you described. I know one was a construction worker who dropped his saw in the water and he automatically reflexed to get it. One had something to do with some idiot had a hot tub on his dock when 240 volts came through the dock into the water via a swimmer who grabbed the metal dock. I would bet that the dock was not grounded properly to a ground rod. To me the key here is that electricity does not take the shortest path to source but takes the path of least resistance. From what I've read the NEC is somewhat at conflict with applications in non-conforming locations. Personally, I live on the lake but don't even have a dock and if I did I would rather it not be wired for electricity but still would have a ground rod bonded to it. This would be to prevent shock to swimmers in the event someone used an extension cord for a battery charger, light, or any other appliance.
The idea that there's no such thing as voltage leaks is just wrong. There is no such thing as an absolute insulator. All an insulator does is offer a very good or acceptable amount of resistance. If glass and ceramics (very good insulators) did not conduct electricity then we would not have resistors and transistors, i.e. they leak electricity. In a sense even rubber is a very good conductor of electricity if you remember the old experiment with static electricity and pocket combs... and that Tesla thingy with the big rubber band can give you a hell of a few thousand volts shock.
You'd be surprised at how many docks I've seen with no more protection than ordinary house wiring and far worse. Read the links I've posted concerning docks. I may get some terms wrong or confuse current and voltage but the detail is not in the current/voltage from the distribution point. The important item is in the ground to the dock. The voltage drop causing the tickle is from the losses due to the distance these wires travel, (especially if the earth ground wire goes hundreds of feet back to the switch box. Suppose this were dc. An electron would have to travel from the battery on the "hot" all the way back down the neutral wire to the panel where earth ground is connected then back down the "ground wire" to the dock. It would have to travel 3 times the distance as it would on only a single wire. This difference in travel time and the losses due to whatever causes those losses... I'll call it friction as an analogy to a mechanical device... would result in a difference in potential or current or whatever the correct term is. This results in a measurable difference in voltage just as I have proven to myself when I put one lead of my volt meter in the water and touched the other to the dock I worked on. For all I know it could have been differences due to stray voltages between the dock and distribution panel but the fact is that there was a voltage difference and I've seen it and heard of this several times. I am not new at this.) The "voltage drop" I'm seeing is in the earth ground wire when it goes back to the panel, not the wires carrying the service voltage/current to and from the dock.
At the dock the potential will be different than it will be at the other end. I can only explain this in layman's terms because I am not accustomed to the technical jargon. See the link I posted to the electrical-contractor.net thread. It is a very "techy" discussion. I have to strain a little to follow but I do understand it.